BIOLOGICAL TECHNIQUES
INSECT
COLLECTION TECHNIQUES
1. Sweep net sampling
Collections of flying insects, or those
inhabiting foliage, can be made using a sweep net. Several types of nets are available,
with standard sizes being either 30.5 cm (12 in) or 38 cm (15 in) diameter.
Aerial nets (net on the right) have an open mesh collection bag and are used mainly
to capture flying insects, although they can be swept through light vegetation
such as tall grass. Beating nets (net on the left) are made from canvas and are
used to sweep through vegetation that could snag and tear a mesh bag. A sweep
is a single back and forth sweep covering a 1500 to 1800 arc.
Collected insects can be identified and counted live in the net, or placed in a
container with a piece of paper towel soaked with non-acetone nail polish
remover to kill them to facilitate counting.
2. Leaf litter sampling
Insects that inhabit leaf litter or mulch
can be surveyed by placing some of this material in an apparatus know as a
Berlese-Tullgren funnel, which is designed to separate insects from the litter.
A simple funnel can be constructed by removing the bottom from a potable water
bottle and placing a piece of 0.6 mm (1/4 in) mesh hardware cloth inside the
neck of the bottle. The inverted bottle should be supported over a container to collect the
insects that come out of the litter. To facilitate the movement of insects from
the litter, a 15W to 25W bulb placed over the funnel will cause the insects to
move deeper into the litter, through the screen, and into the container. The
preservative in the container can be 75 to 80% ethanol.
3. Light trap sampling
Although insects have good color vision,
they do not see the same wavelengths of light as humans. The human eye can
typically distinguish colors ranging from red (760 nm [nanometers]) to purple (380 nm), while
it has been shown that most insects see colors from yellow / green (550 nm) to
ultraviolet [UV] (340 nm). Since many nocturnal insects are attracted to UV,
trapping or killing devices have been developed that use UV bulbs to attract
insects either to a collection container (we call these light traps) or to an electric
grid (we call these bug zappers). Because insects do not perceive light in the red
to yellow range, we use yellow bug lights outdoors to reduce the number of insects
attracted to areas around our homes. Since most humans see relatively well under
yellow light, these bulbs allow us to see while not attracting many insects. A simple light trap design is illustrated
below. It’s construction is also described. Traps can be built either as single units
or as a series of lights that can be used to allow comparison among bulbs of different
colors, from several manufacturers, or having different wattage.
4. Pitfall trapping.
Pitfall traps are collect populations of
insects and other arthropods living on the ground surface. Typically, traps are
set up and allowed to collect insects for a minimum of 24 hours. The basic trap
consists of a container set into the ground so that the upper rim is flush with
the ground surface. Since many insects are predators and will eat other insects
in the trap, a solution to kill and preserve insects entering the trap is used.
5. Aquatic insect collections using D-framed
nets
These nets have a opening with a flat
side (the D part) (at left). They can be used like a kick-net, with the flat side
placed on the stream bottom so that it collects organisms dislodged when submerged
objects upstream are disturbed. It also can be used more like a dip net and
scraped along submerged objects to dislodge and collect organisms, or the flat
side can be pulled across the bottom sediments of a pond or stream to sample
organisms in that habitat.
Note: This post is still
undergoing developments. Please update constantly.
The 2014 edition of the Biosafety workshop held at the International Centre for Genetic Engineering and Biotechnology, Trieste, Italy which began on Monday has started winding down. The workshop which theme is the Role of Science in GMO Decision Making has been of tremendous interest and motivation for the Centre, the Faculty and Participants. 